Use-cases can be rewritten as tests (I can send my own unit-test if needed)

Also I've two related things to discuss.
1) First is &-syntax. Is it possible to change ruby-interpeter in such a way that &:proc could be at any place. matrix.pmap(&:join,' ') is much prettier than matrix.join(' ',&:join) What is the reason behind this restriction? And if one can remove this restriction, we'd have new nice syntax.
2) I'm not very experience in functional programming with curry etc, but it seems to me that currying proc without supplying first argument(self) can be common task when &:meth syntax is in play. If so, may be my curry_except_self(*args) also should be included in ruby.

I reject the original idea of #pmap which might be read as 'parallel map' or 'parametric map' or something else.
The idea of adding parameter to block with argument specified e.g. a.map(&:to_s.(2)) is interesting,
but it must be proposed in separated issue.